The study of the gills of 359 Tilapia zillii, which were caught between August 2004 and July 2005, have been investigated in the Ayame man-made lake (Côte d'Ivoire), so as to collect first data on the population dynamics of the Monogeneans parasites in a wild population. Standard methods of parasitological examination were used for identification of Monogenean species. Four Cichlidogyrus species were identified on the gills of host fish: C. digitatus, C. aegypticus, C. vexus and C. yanni. Rates of parasites species were calculated. Prevalence and mean intensity of the Monogenean showed clear fluctuations throughout the year. The parasites were found to settle more on the larger host fish. However, no sex effect was observed on the infestation of T. zillii by the Monogeneans. Throughout the period of study, all parasite species were present, because the recruitment of these organisms, although relatively low, is continuous; this logically results in their accumulation in this fish species.